Method for manufacturing a cooling plate for a metallurgical furnace

ABSTRACT

A method for manufacturing a cooling plate ( 10 ) for a metallurgical furnace comprising the steps of providing a slab ( 11 ) of metallic material, the slab ( 11 ) having a front face ( 14 ), an opposite rear face ( 16 ) and four side edges; and providing the slab ( 11 ) with at least one cooling channel ( 30 ) by drilling at least one blind borehole ( 40 ) into the slab ( 11 ), wherein the blind borehole ( 40 ) is drilled from a first edge ( 22 ) towards an opposite second edge ( 24 ). In accordance with an important aspect of the present invention, the method comprises the further steps of deforming the slab ( 11 ) in such a way that a first edge region ( 46 ) of the slab ( 11 ) is at least partially bent towards the rear face ( 16 ) of the slab ( 11 ); and machining excess material from the front and rear faces ( 14, 16 ) of the slab ( 11 ) to produce a cooling plate ( 10 ) having a panel-like body ( 12 ) wherein an opening to the cooling channel ( 30 ) is located in the rear face ( 16 ).

TECHNICAL FIELD

The present invention generally relates to a method for manufacturing acooling plate for a metallurgical furnace.

BACKGROUND

Such cooling plates for a metallurgical furnace, also called staves, arewell known in the art. They are used to cover the inner wall of theouter shell of the metallurgical furnace, as e.g. a blast furnace orelectric arc furnace, to provide: (1) a heat evacuating protectionscreen between the interior of the furnace and the outer furnace shell;and (2) an anchoring means for a refractory brick lining, a refractoryguniting or a process generated accretion layer inside the furnace.Originally, the cooling plates have been cast iron plates with coolingpipes cast therein. As an alternative to cast iron staves, copper staveshave been developed. Nowadays, most cooling plates for a metallurgicalfurnace are made of copper, a copper alloy or, more recently, of steel.

Different production methods have been proposed for copper stavecoolers. Initially, an attempt was made to produce copper staves bycasting in moulds, the internal coolant channels being formed by a sandcore in the casting mould. However, this method has not proved to beeffective in practice, because the cast copper plate bodies often havecavities and porosities, which have an extremely negative effect on thelife of the plate bodies. The mould sand is difficult to remove from thechannels and the channels are often not properly formed.

A cooling plate made from a forged or rolled copper slab is known fromDE 2 907 511 C2. The coolant channels are blind boreholes introduced bydeep drilling the rolled copper slab. The blind boreholes are sealed offby welding in plugs. Then, connecting bores are drilled from the rearside of the plate body into the blind boreholes. Thereafter, connectionpipe-ends for the coolant feed or coolant return are inserted into theseconnecting bores and welded to the stave body. With these coolingplates, the above-mentioned disadvantages related to casting areavoided. In particular, cavities and porosities in the plate body arevirtually precluded. The above manufacturing method is howeverrelatively expensive both in labour and material. Furthermore, due toconsiderable mechanical and thermal stress to which the stave cooler isexposed, the different welded connection joints are critical as regardsfluid tightness. In addition, since the channels are integral with thestave body, there is only one level of separation between the coolantand the furnace interior, i.e. if the stave body cracks open, coolantwill leak. A leakage of coolant fluid into the furnace however leads toa significant risk of explosion and should therefore be avoided at allcost.

BRIEF SUMMARY

The invention provide an improved method for manufacturing a coolingplate for a metallurgical furnace, wherein the method does not displaythe aforementioned drawbacks.

A method for manufacturing a cooling plate for a metallurgical furnacein accordance with the present invention comprises the steps ofproviding a slab of metallic material, the slab having a front face, anopposite rear face and four side edges; and providing the slab with atleast one cooling channel by drilling at least one blind borehole intothe slab, wherein the blind borehole is drilled from a first edgetowards an opposite second edge. In accordance with an important aspectof the present invention, the method comprises the further steps ofdeforming the slab in such a way that a first edge region of the slab isat least partially bent towards the rear face of the slab; and machiningexcess material from the front and rear faces of the slab to produce acooling plate having a panel-like body wherein an opening to the coolingchannel is located in the rear face.

By bending the slab towards the rear face and subsequently machiningexcess material from the front and rear faces of the slab, the openingto the cooling channel is located in the rear face. Compared to theprior art method, as e.g. described in DE 2 907 511 C2, it is no longernecessary to seal off the opening to the cooling channel in the firstedge by welding in a plug. Nor is it necessary to drill a connectingbore between the rear face and the cooling channel to access the coolingchannel in the first edge region. The removal of these process stepsreduces both labour and material costs.

More importantly, however, the absence of the plug provides a morereliant cooling plate. Indeed, as the cooling plate is exposed toconsiderable mechanical and thermal stress, in particular in the edgeregions of the cooling plate, the plug has to be considered as a weakpoint. If the weld of the plug deteriorates, fluid tightness of thecooling channel can no longer be guaranteed and coolant could leak fromthe cooling channel into the furnace. Such leakage of coolant fluid intothe furnace should however be avoided at all cost as it may lead to asignificant risk of explosion. As no such plug is welded to the coolingplate manufactured according to the method of present invention, therisk of a leakage occurring through such a plug is avoided. Furthermore,the cooling plate manufactured according to the method of presentinvention also presents a more important material thickness on the frontface in the first edge region, as compared to cooling platesmanufactured according prior art methods. The increased materialthickness also contributed to a longer lifetime of the cooling plate.

Preferably, after machining excess material from the front and rearfaces of the slab, the method comprises the additional step of forminggrooves and intermittent lamellar ribs in the front face of thepanel-like body for anchoring a refractory brick lining.

To warrant a good anchoring function of the lamellar ribs and groovesstructure on the front face of the cooling plate and a good thermal formstability of the cooling plate, the grooves are advantageously formedwith a width that is narrower at an inlet of the groove than at a baseof the groove. The grooves may e.g. be formed with dovetailcross-section.

Preferably, the method comprises the additional step of providing aconnection pipe for each cooling channel formed in the panel-like body;aligning one end of each connection pipe with an opening to therespective cooling channel arranged in the rear face of the panel-likebody; and connecting the connection pipes to the rear face of thepanel-like body so as to create a fluid connection between eachconnection pipe and its associated cooling channel.

An adapter may be arranged between the panel-like body and theconnection pipe, the adapter having the form of a hollow truncated cone.The smaller base of the adapter may have a diameter adapted forconnection to the connection pipe. The larger base of the adapter isdimensioned so as to cover the whole opening of the cooling channel inthe rear face. Indeed, due to the bending of the cooling channel and thesubsequent machining of the rear face, the cooling channel may have anelongated opening in the rear face. The larger base of the adapterallows to ensure that a leakage at the rear face of the cooling platecan be avoided.

Preferably, the rear face of the panel-like body, the connection pipeand, if applicable, the adapter are connected together through solderingor welding.

According to a first embodiment of the invention, the method comprisesthe steps of providing the slab with a first cooling channel by drillinga first blind borehole into the slab, wherein the first blind boreholeis drilled from the first edge towards the second edge; and providingthe slab with a second cooling channel by drilling a second blindborehole into the slab, wherein the second blind borehole is drilledfrom the first edge towards the second edge. The first and secondcooling channels are arranged in such a way that their ends in a secondedge region meet and form a fluid communication between the first andsecond cooling channels.

The first and second blind boreholes are both drilled from the firstedge towards the second edge at an angle with respect to each other, insuch a way that their ends meet in the second edge region. The resultingfirst and second cooling channels thereby form a combined “V”-shapedcooling channel, wherein coolant flows through one of the coolingchannels towards the second edge region and then, through the other oneof the cooling channels, back to the first edge region. Such a“V”-shaped cooling channel allows both the inlet connection pipe and theoutlet connection pipe to be arranged in the first edge region.

According to a second embodiment of the invention, the method comprisesthe steps of providing the slab with a first cooling channel by drillinga first blind borehole into the slab, wherein the first blind boreholeis drilled from the first edge towards the second edge; and providingthe slab with a second cooling channel by drilling a second blindborehole into the slab, wherein the second blind borehole is drilledfrom the second edge towards the first edge. The first and secondcooling channels are arranged in such a way that their ends meet andform a fluid communication between the first and second coolingchannels.

The first and second blind boreholes are drilled from opposite edgestowards a central region of the slab, in such a way that their ends meetin the central region. The resulting first and second cooling channelsthereby form a combined cooling channel extending from the first edge tothe second edge. This is of particular importance when a cooling platewith particularly important height is to be manufactured. Indeed, blindboreholes can only be drilled up to a particular depth. If the coolingchannel is to exceed this depth, a second blind borehole is generallydrilled from the opposite side. In this embodiment, both the first edgeregion and the second edge region are bent towards the rear face beforeremoving excess material from the slab. Two cooling channel openings arethereby formed in the rear face without resorting to the necessity toprovide plugs at either end of the cooling channel.

According to a third embodiment of the invention, the method comprisesthe steps of providing the slab with a first cooling channel by drillinga first blind borehole into the slab, wherein the first blind boreholeis drilled from the first edge towards the second edge, wherein an endof the first blind borehole is arranged in a second edge region of theslab; and, in the second edge region, drilling a connecting boreextending from the rear face of the slab to the end of the first blindborehole and forming a fluid communication between the first coolingchannel and the connecting bore.

In the first edge region, the slab is bent towards the rear face and anopening to the cooling channel is thereby formed in the rear face. Inthe second edge region on the other hand, a connecting bore is providedfor forming second opening to the cooling channel. The formation of thissecond opening to the cooling channel essentially corresponds the methodused in the prior art methods. This embodiment is adapted for connectingan inlet connection pipe in the first edge region and an outletconnection pipe in the second edge region.

Preferably, the cooling plate is made of at least one of the followingmaterials: copper, a copper alloy or steel.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention will now be described, by way ofexample, with reference to the accompanying drawings, in which:

FIG. 1 is a schematic cross-section through a slab according to a firststep of the method for manufacturing a cooling plate in accordance withthe present invention;

FIG. 2 is a schematic cross-section through a slab according to a secondstep;

FIG. 3 is a schematic cross-section through a slab according to a thirdstep; and

FIG. 4 is a schematic cross-section through a slab according to a fourthstep.

DETAILED DESCRIPTION

Cooling plates are used to cover the inner wall of an outer shell of ametallurgical furnace, as e.g. a blast furnace or electric arc furnace.The cooling plates form: (1) a heat evacuating protection screen betweenthe interior of the furnace and the outer furnace shell; and (2) ananchoring means for a refractory brick lining, a refractory guniting ora process generated accretion layer inside the furnace.

Referring now to the Figures, it will be noted that the cooling plate 10is formed from a slab 11 e.g. made of a cast or forged body of copper, acopper alloy or steel into a panel-like body 12. This panel-like body12, which is more closely described by referring to FIG. 4 has a frontface 14, also referred to as hot face, which will be facing the interiorof the furnace, and a rear face 16, also referred to as cold face, whichwill be facing the inner surface of the furnace wall. Referring to FIG.4, the panel-like body 12 generally has the form of a quadrilateral witha pair of long edges (not shown) and a pair of short first and secondedges 22, 24. Most modern cooling plates have a width in the range of600 to 1300 mm and a height in the range of 1000 to 4200 mm. It willhowever be understood that the height and width of the cooling plate maybe adapted, amongst others, to structural conditions of a metallurgicalfurnace and to constraints resulting from their fabrication process.

The cooling plate 10 further comprises connection pipes 26, 28 for acooling fluid, generally water. These connection pipes 26, 28 areconnected from the rear side of the panel-like body 12 to coolingchannels 30 arranged within the panel-like body 12. As seen in FIG. 4,these cooling channels 30 extend through the panel-like body 12 inproximity of the rear face 16. According to the proposed method ofmanufacturing, which will be described in further detail below, suchcooling channels 30 are formed by drilling. Each cooling channel 30 isnormally provided with an appropriate inlet connection pipe 26, throughwhich the cooling fluid is fed into the cooling channel 30, and/oroutlet connection pipe 28, through which the cooling fluid leaves thecooling channel 30.

Referring further to FIG. 4, it will be noted that the front face 14 issubdivided by means of grooves 32 into lamellar ribs 34. The grooves 32,laterally delimiting the lamellar ribs 34, may be milled into the frontface 14 of the panel-like body 12. The lamellar ribs 34 extend parallelto the first and second edges 22, 24, from a first long edge (not shown)to a second long edge (not shown) of the panel-like body 12. They areperpendicular to the cooling channels 30 in the panel-like body 12. Whenthe cooling plate 10 is mounted in the furnace, the grooves 32 andlamellar ribs 34 are arranged horizontally. They form anchorage meansfor anchoring a refractory brick lining, a refractory guniting or aprocess generated accretion layer to the front face 14.

In order to warrant an excellent anchoring for a refractory bricklining, a refractory guniting material or a process formed accretionlayer to the front face 14, it should be noted that the grooves 32 havea dovetail (or swallowtail) cross-section, i.e. the inlet width of agroove 32 is narrower than the width at its base. The mean width of alamellar rib 34 is preferably smaller than the mean width of a groove32. Typical values for the mean width of a groove 32 are e.g. in therange of 40 mm to 100 mm. Typical values for the mean width of alamellar rib 34 are e.g. in the range of 20 mm to 40 mm. The height ofthe lamellar ribs 34 (which corresponds to the depth of the grooves 32)represents generally between 20% and 40% of the total thickness of thepanel-like body 12.

The method for manufacturing the cooling plates 10 will now be moreclosely described by referring to FIGS. 1 to 4, which represent thecooling plates 10 at different key steps of the manufacturing method. Ina first step, shown in FIG. 1, a slab 11 e.g. made of a cast or forgedbody of copper, a copper alloy or steel is provided. Such a slab has agenerally quadrilateral form with a front face 14, rear face 16, a pairof long edges (not shown) and a pair of short first and second edges 22,24. It should be noted that the slab 11 has dimensions exceeding thedesired dimensions of the panel-like body 12. At least one blindborehole 40 is drilled from the first edge 22 into the slab 11 andextends to a second edge region 42. The blind borehole 40 has an end 44arranged in the second edge region 42. In a subsequent step of themethod, illustrated by FIG. 2, the slab 11 is deformed in such a waythat a first edge region 46 is bent towards the rear face 16 of the slab11. This results in a corresponding bending of the blind borehole 40.The bending angle a between a central axis 50 of the unbent blindborehole 40 and a central axis 52 of the blind borehole 40 at the firstedge 22 may be between 30 and 45 degrees. This bending angle a shouldhowever not be understood as limiting. The bending angle a may e.g. varyconsiderably depending on the thickness of the slab 11 or the diameterof the blind borehole 40.

After the slab 11 is deformed, excess material is removed from the slab11 along the cutting lines indicated by dotted lines 55 in FIG. 2. Theresulting panel-like body 12, shown in FIG. 3, is again of a generallyquadrilateral form with a front face 14, rear face 16, a pair of longedges (not shown) and a pair of short first and second edges 22, 24. Acooling channel 30, formed by the blind borehole 40, is formed in thepanel-like body 12 generally parallel to the rear face 16. In the firstedge region 46, the cooling channel 30 is bent and opens up into therear face 16.

According to one embodiment of the present invention, the panel-likebody 12 can be provided with a bore 60 in the second edge region 42,extending from the cooling channel 30 to the rear face 16.

After machining excess material from the slab 11, the resultingpanel-like body 12 is further subjected to a milling step, whereingrooves 32 and intermittent lamellar ribs 34 are formed in the frontface 14 of the panel-like body 12. As explained above, these grooves 32and ribs 34 form anchorage means for anchoring a refractory bricklining, a refractory guniting or a process generated accretion layer tothe front face 14 of the cooling plate 10.

Finally, connection pipes 26, 28 are connected to the rear face 16 ofthe panel-like body 12. An inlet connection pipe 26 is fluidly connectedto the opening of the cooling channel 30 in the first edge region 46 forfeeding cooling fluid into the cooling channel 30. An outlet connectionpipe 28 is fluidly connected to the bore 60 in the second edge region 42for evacuating cooling fluid from the cooling channel 30.

1. A method for manufacturing a cooling plate for a metallurgicalfurnace, said method comprising the steps of: providing a slab ofmetallic material, said slab having a front face, an opposite rear faceand four side edges; and providing said slab with at least one coolingchannel by drilling at least one blind borehole into said slab, whereinsaid blind borehole is drilled from a first edge towards an oppositesecond edge; wherein the method further comprises the steps of:deforming said slab in such a way that a first edge region of said slabis at least partially bent towards said rear face of said slab; andmachining excess material from said front and rear faces of said slab toproduce a cooling plate having a panel-like body wherein an opening tosaid cooling channel is located in said rear face.
 2. The method asclaimed in claim 1, wherein, after machining excess material from saidfront and rear faces of said slab, the method comprises the additionalstep of: forming grooves and intermittent lamellar ribs in said frontface of said panel-like body for anchoring a refractory brick lining. 3.The method as claimed in claim 2, wherein the grooves are formed with awidth that is narrower at an inlet of the groove than at a base of thegroove.
 4. The method as claimed in claim 3, wherein the grooves areformed with dovetail cross-section.
 5. The method as claimed in claim 1,wherein the method comprises the additional step of: providing aconnection pipe for each cooling channel formed in said panel-like body;aligning one end of each connection pipe with an opening to therespective cooling channel arranged in the rear face of the panel-likebody; and connecting said connection pipes to said rear face of saidpanel-like body so as to create a fluid connection between eachconnection pipe and its associated cooling channel.
 6. The method asclaimed in claim 5, wherein an adapter is arranged between saidpanel-like body and said connection pipe, said adapter having the formof a hollow truncated cone.
 7. The method as claimed in claim 5, whereinsaid rear face of said panel-like body, said connection pipe and, ifapplicable, said adapter are connected together through soldering orwelding.
 8. The method as claimed in claim 1, further comprising thesteps of: providing said slab with a first cooling channel by drilling afirst blind borehole into said slab, wherein said first blind boreholeis drilled from said first edge towards said second edge; providing saidslab with a second cooling channel by drilling a second blind boreholeinto said slab, wherein said second blind borehole is drilled from saidfirst edge towards said second edge; wherein said first and secondcooling channels are arranged in such a way that their ends in a secondedge region meet and form a fluid communication between said first andsecond cooling channels.
 9. The method as claimed in claim 1, furthercomprising the steps of: providing said slab with a first coolingchannel by drilling a first blind borehole into said slab, wherein saidfirst blind borehole is drilled from said first edge towards said secondedge; providing said slab with a second cooling channel by drilling asecond blind borehole into said slab, wherein said second blind boreholeis drilled from said second edge towards said first edge; wherein saidfirst and second cooling channels are arranged in such a way that theirends meet and form a fluid communication between said first and secondcooling channels.
 10. The method as claimed in claim 1, furthercomprising the steps of: providing said slab with a first coolingchannel by drilling a first blind borehole into said slab, wherein saidfirst blind borehole is drilled from said first edge towards said secondedge, wherein an end of said first blind borehole is arranged in asecond edge region of said slab; in said second edge region, drilling aconnecting bore extending from said rear face of said slab to said endof said first blind borehole and forming form a fluid communicationbetween said first cooling channel and said connecting bore.
 11. Themethod as claimed in claim 1, wherein said cooling plate is made of atleast one of the following materials: copper, a copper alloy or steel.